Zapping does work sometimes. Personally I have only tried this once and to my amazement it worked!! My success was just a cheap Chinese magic eye but it does give you a over whelming feeling of resurrecting the dead! One thing I would have tried, bit late now! but remove the heater link to ground, worth a try.
A bit of arm-chair quarterbacking as we would call it over here, but couldn't you remove the connection between the cathode lead and the heater lead in the power supply and let the short be that connection? The isolation of the transformer winding allows the filament supply to float at cathode potential in either case. (?) I had an interesting battle with an HP 1349A display for my 8753A VNA that had lots of very intermittent issues mainly with the Z output, turned out to be cracked solder joints at the pins on the circuit boards that the CRT wires plug on to. Thank you for an interesting video. Hope you have a happy Christmas - Regards, David
Have you ever had any experience with Sony Trinitrons, specifically BVMs and PVMS? My BVM-D20 flashes pink randomly but consistently. I was told that it's a cathode to heater short that could be causing it. When I moderately tap on the glass part of the tube's neck, the pink flicker tends to go away but then returns.
Hows about trying RF welding to cure the of heater? I tried it years ago from an article in Television magazine using the high voltage waveform from the lineoutput valve top cap (Pl504) it worked but not for long.🤔
basically, what happened to your filament, is that the oxide coating on the wire cracked due to heating cooling cycles, or arcing, allowing the wire inside the oxide shell to expand enough across the gap to cause a hot short. other then mechanical repair of the filament i do not know how to fix such a failure. Doing so is a rather expensive and time consuming process though.
I would have removed the jumper, and replaced it with a 50 to 100 ohm resistor. That would have provided a higher impedance connection but still effectively limited the heater to cathode voltage. If (when) the internal short came back, the current through the resistor path would not have been enough to overload the flyback transformer.
Darn that's unfortunate. Never worked with CRT's, but I'm guessing it probably has a coated tungsten heater using AlO3 which is an insulator. Sometimes as the tungsten wire ages it begins to sag. You might have seen tungsten sag in an old incandescent lamp before it goes open. Then the alumina coating will crack and flake off. I'm speaking off the cuff here, my knowledge of CRT's is not good. Some of the high power transmitting tubes used what was called a "pusher spring arrangement" on the thoriated tungsten cathode to help keep it under slight pressure (and because of the thermal expansion of the wire) over the life of the tube. Example is the 4-1000A. Still, I think you will be able to pick up a another used spare in the future if you hawk it out. Merry Merry Simon.
It's a real shame about the heaters, but it was already very ill. That heater would of never behaved itself, i don't suppose giving the heater it's own isolated transformer would of worked any better eather. I'm not a valve or tube man, but i did make a tube blaster back in 92, so i diddled with old delta gun crts a bit. I had similar ideas to you simon, the cap voltage zapping jumped out of the transistor whisker zapping lol. Is that crt a very special one, does the test gear have a video signal that could feed something else. Or is it super special scanning frequencys that's incompatable with everything else.
Would it not have been possible to leave the heater / cathode short alone and simple run the heater from an isolated source, small transformer or even a few turns of wire around the line out transformer. I like your video`s. Complements, Chris.
Yes that was an option. Unfortunately by the time thus fault showed up I had come to the end of my tether with the whole machine. This was the 2nd Crt that died.
Hello Simon. Is it viable to get the tube re gunned ?? ...... I did contemplate re gunning the CRT in my HP8562e Spectrum analyzer but splashed out several hundreds on the tft option in the end. only because I use it regularly. Nice upload... keep em coming .... Oh! seasons greetings all. :-)
@@SoddingaboutSi yup. everyone is a general after the battle, as it where. i know i have done my fair share of stupid things and will likely continue to do the occasional stupid., just like everyone else. For a situation like the filament blasting, i use the term "Brain AFK", AFK being an abbreviation of "away from keyboard"
Darn, shame. There is a technique of putting a high voltage across the the heater (current limited) and tap the neck to hopefully weld the heater. But it needs enough heater wire left to get the ends to come into contact.
@@SoddingaboutSi a few places still have the knowledge and equipment to do so. among some private individuals like glassslinger and me. I however lack the glass blowing ability's of glass slinger.
@@SoddingaboutSi well, with some crts, you can get an extra bit of life from them by changing their operating values. as long as the filament is good, the tube should light
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Great video Simon very interesting. You cannot win them all but you gave it a good effort. Thanks regards Chris
Cheers Chris. Worth a try.
As we say "A valiant effort but a miserable failure" - don't feel bad Simon, I've been there done that and have the tee shirt! Happy holidays!
Thanks Dino, the same to you.
Well it was worth the attempt anyway, Simon.
Exactly. It's buggered so worth a shot.
Zapping does work sometimes. Personally I have only tried this once and to my amazement it worked!! My success was just a cheap Chinese magic eye but it does give you a over whelming feeling of resurrecting the dead!
One thing I would have tried, bit late now! but remove the heater link to ground, worth a try.
excellent, as always
beautiful CRT
Worth a go. I understand these electro- statically deflected tubes are very fragile in any case. Commiserations anyway but good effort.
Excellent vid ty
A bit of arm-chair quarterbacking as we would call it over here, but couldn't you remove the connection between the cathode lead and the heater lead in the power supply and let the short be that connection? The isolation of the transformer winding allows the filament supply to float at cathode potential in either case. (?) I had an interesting battle with an HP 1349A display for my 8753A VNA that had lots of very intermittent issues mainly with the Z output, turned out to be cracked solder joints at the pins on the circuit boards that the CRT wires plug on to. Thank you for an interesting video. Hope you have a happy Christmas - Regards, David
Have you ever had any experience with Sony Trinitrons, specifically BVMs and PVMS? My BVM-D20 flashes pink randomly but consistently. I was told that it's a cathode to heater short that could be causing it. When I moderately tap on the glass part of the tube's neck, the pink flicker tends to go away but then returns.
Sounds like loss of vacuum?
Hows about trying RF welding to cure the of heater? I tried it years ago from an article in Television magazine using the high voltage waveform from the lineoutput valve top cap (Pl504) it worked but not for long.🤔
basically, what happened to your filament, is that the oxide coating on the wire cracked due to heating cooling cycles, or arcing, allowing the wire inside the oxide shell to expand enough across the gap to cause a hot short. other then mechanical repair of the filament i do not know how to fix such a failure. Doing so is a rather expensive and time consuming process though.
I would have removed the jumper, and replaced it with a 50 to 100 ohm resistor. That would have provided a higher impedance connection but still effectively limited the heater to cathode voltage. If (when) the internal short came back, the current through the resistor path would not have been enough to overload the flyback transformer.
Pity, it was worth a shot as there was nothing to lose, it’s no more broken than it was before you tried... dead is dead.
Darn that's unfortunate. Never worked with CRT's, but I'm guessing it probably has a coated tungsten heater using AlO3 which is an insulator. Sometimes as the tungsten wire ages it begins to sag. You might have seen tungsten sag in an old incandescent lamp before it goes open. Then the alumina coating will crack and flake off. I'm speaking off the cuff here, my knowledge of CRT's is not good. Some of the high power transmitting tubes used what was called a "pusher spring arrangement" on the thoriated tungsten cathode to help keep it under slight pressure (and because of the thermal expansion of the wire) over the life of the tube. Example is the 4-1000A. Still, I think you will be able to pick up a another used spare in the future if you hawk it out. Merry Merry Simon.
It's a real shame about the heaters, but it was already very ill.
That heater would of never behaved itself, i don't suppose giving the heater it's own isolated transformer would of worked any better eather.
I'm not a valve or tube man, but i did make a tube blaster back in 92, so i diddled with old delta gun crts a bit.
I had similar ideas to you simon, the cap voltage zapping jumped out of the transistor whisker zapping lol.
Is that crt a very special one, does the test gear have a video signal that could feed something else.
Or is it super special scanning frequencys that's incompatable with everything else.
Must be an interesting place you work at. Can you tell us what is it?
Yes. This is a Cathode Ray Tube from a HP display unit.
@@SoddingaboutSi Sorry, my question wasn't very clear. I was referring to your day job. Happy holidays!
My main job is a power supply company. This is just my hobby at home. Happy Christmas!
Would it not have been possible to leave the heater / cathode short alone and simple run the heater from an isolated source, small transformer or even a few turns of wire around the line out transformer. I like your video`s. Complements, Chris.
Yes that was an option. Unfortunately by the time thus fault showed up I had come to the end of my tether with the whole machine. This was the 2nd Crt that died.
Hello Simon. Is it viable to get the tube re gunned ?? ...... I did contemplate re gunning the CRT in my HP8562e Spectrum analyzer but splashed out several hundreds on the tft option in the end. only because I use it regularly. Nice upload... keep em coming .... Oh! seasons greetings all. :-)
There are very few , if any CRT restorers still in business unfortunately.
blasting the filament was a stupid idea. the wire used in it is a few microns in diameter, so even a small cap discharge will break the wire.
We all do stupid things sometimes.
@@SoddingaboutSi yup. everyone is a general after the battle, as it where. i know i have done my fair share of stupid things and will likely continue to do the occasional stupid., just like everyone else.
For a situation like the filament blasting, i use the term "Brain AFK", AFK being an abbreviation of "away from keyboard"
Darn, shame. There is a technique of putting a high voltage across the the heater (current limited) and tap the neck to hopefully weld the heater. But it needs enough heater wire left to get the ends to come into contact.
Seriously I’m the only one to notice the Ben Sherman vest. Mod.
Nice video. Please do not junk the rest of the machine - someone might need the parts!
you could also just rebuild the cathode. though it would require glass blowing knowledge to do.
There is no one who restores CRT's any more. I have option of a LCD replacement but it's not worth the cost.
@@SoddingaboutSi a few places still have the knowledge and equipment to do so. among some private individuals like glassslinger and me. I however lack the glass blowing ability's of glass slinger.
@@lbochtler I did find anothet complete displsy with a good gun. Not sure of its emissions though.
@@SoddingaboutSi well, with some crts, you can get an extra bit of life from them by changing their operating values. as long as the filament is good, the tube should light
Such a shame, worth a try though. Had a B&K tube rejuvenator at Panasonic. Probably should have brought it home for what it's worth. Hey ho.
Try to move the cathode whith a strong magnet,may be....!
Thats a good point. Unfortunately i blew the heater